This invention relates to a method for adjusting the beam conditions of the charged particle beam and a charged particle beam apparatus, or in particular to a charged particle beam adjustment method for adjusting the angle and distortion and calibrating the angle of a tilted beam and a charged particle beam apparatus.
In the charged particle beam apparatus of which a typical example is the scanning electron microscope (SEM), a thinly focused charged particle beam is scanned on a sample to obtain the desired information such as a sample image from the sample. The resolution of this charged particle beam apparatus has been improved every year. At the same time, it has recently come to be considered necessary to obtain a tilted image of the sample by tilting the charged particle beam with respect to the sample. To obtain a tilted image of a sample, it is common practice to tilt a sample stage. For preventing the shift of the visual field at high magnification or obtaining a tilted image of a sample at high speed, however, it is more reasonable to tilt the charged particle beam with respect to the sample rather than to tilt the sample stage mechanically.
JP-A-55-48610 (U.M.) and JP-A-2-33843, for example, disclose a technique for radiating a tilted beam, in which the charged particle beam is incident out of axis of an objective lens and the beam is tilted utilizing the focusing action or the restoration action of the objective lens.
The conventional techniques described above, however, refer to nothing about a method of angle adjustment of a tilted beam, a method of automating the adjustment, a method of correcting the image distortion at the time of tilting the beam or a method of automatic adjustment thereof. In order to tilt the beam accurately, it is necessary to correct the tilt angle and the image distortion at the time of tilting the beam for each direction. Also, the adjustment is required to be easy and efficient.